Technical Abstract: Tillage as a source of erosion
Tillage erosion is the downslope movement of soil by tillage. During tillage, soil is lifted and gravity moves soil downslope. Soil movement by tillage increases with slope steepness. However, net soil transport by tillage is determined by the change in slope. Soil movement by tillage very slowly levels the land surface. Soil is removed from areas where slope is increasing (convex) and deposited in areas where slope is decreasing (concave).
Unlike water erosion, tillage erosion is not strongly affected by slope length. Therefore, in hilly regions that have many changes in slope, tillage erosion can be the dominant erosive force. This applies in the eastern Dakotas, western Minnesota, and throughout the Prairie Pothole Region.
Conditions that influence tillage erosion
Tillage erosion is greatest with frequent, intensive tillage. Soil movement by tillage is affected the tillage operation (implement design; depth, speed, and direction of tillage), topography (curvature, change in slope, steepness), and soil properties (bulk density, soil texture).
Any implement that lifts the soil will cause tillage erosion. Some secondary operations are as erosive as primary tillage operations.
Soil changes resulting from tillage erosion
Tillage erosion degrades soil quality in upper slope positions. The additive effect of years of combined tillage, water, and wind erosion is shallow topsoil in the upper slope (sometimes with exposed subsoil) and deep topsoil accumulation in depressions.
Erosion changes soil organic matter content, soil texture, water holding capacity, nutrient availability, aeration, pH, and other soil properties that affect productivity.
Productivity changes resulting from tillage erosion
Tillage erosion depletes crop yield in areas of soil loss. In our studies, plant growth and yield was linked to changes in soil properties induced by soil movement by tillage.
We measured yield in an eroded prairie landscape for 4 years (3 years of wheat, 1 year of soybean) and found that grain yields in the most eroded portions of the field were consistently less than half of the yield in non-eroded areas.
Effects on management
In the eastern Dakotas and western Minnesota, long-term tillage has increased the land area with poor-quality topsoil. Crop yields on eroded land reflect soil properties. Approaches to reduce the effects of soil erosion on productivity are being investigated, including precision agriculture and targeted application of manure and other soil amendments.